Question

A student determines the molar mass of acetone

Answer 1

The Formula of Acetone is $C_3H_6O$
To find the Mass Molar of a compound, you add the Atomic weights of it's atoms.
If you check the Periodic table:
Atomic Weight of Carbone C: 12.0107
Atomic Weight of Hydrogen: 1.00794
Atomic Weight of Oxygen: 15.9994 

So, you got:
Total Atomic Weight of Carbone in Acetone: 12.0107 * 3 = 36.0321 
Total Atomic Weight of Hydrogen in Acetone: 1.00794 * 6 = 6.04764
Total Atomic Weight of Oxygen in Acetone = 15.9994 * 1 = 15.9994

Now, you add this numbers
36.0321 + 6.04764 + 15.9994 = 58.07914

So, the Molar Mass of Acetone is 58.09714 g/mol

Hope this Helps :D